CO^SiCHYUA—DITHYRA. xv- 



39. Pectunculus. — Cardo arcuatus, dentibus numerosis. 



Hinge ia a curved line, with numerous teeth. 



*** Cardo dentibvs prhnarifs et lateralibus. 



Hinge with both primary and lateral teetli. 



16. AmPHIDESMA. — Denies primarii cochleariformes. 

 The primary teeth spoon-shaped. 



50. Cyclas. — Deiites primarii minuti divergentes, lateralibus 

 valvce alterius didymis. 

 The primary teeth minute and divergent, with the 

 lateral teeth of one valve double. 



55. ^X&CK.— Denies pi-imarii transversi cienulati, laterlibus valvce 

 alterius didyms. 

 The primary teeth transverse and notched, with 

 the lateral teeth of one valve double. 



34. Myrtea. — Valva altera unidentata cum laterali utrinquh, 



altera bidentata lateralibus obsoletis. 

 In one valve a single tooth and a lateral one each 

 side, in the other valve two teeth with the lateral 

 ones obscure. 



35. Cyprina. — Denies primarii duo vel Ires, laterali remolo. 



The primary teeth two or three, and a remote 

 lateral one. 



31. DoNAX. — Testa ctmcatu, Uiramenlo ad latiis hrevissimuin. 



Shell wedge-shaped, with the ligament at ihe 

 shortet^t side. 



